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Using PolkadotJs with Creditcoin

Install Dependencies

Install PolkadotJs API:

yarn add @polkadot/api

Generating Types from Metadata

If you want to generate types from the chain's metadata you can do the following (adapted from PolkadotJs Typegen Example):

Install @polkadot/typegen and ts-node:

yarn add -D @polkadot/typegen ts-node

To download the chain's metadata:

curl -H "Content-Type: application/json" -d '{"id":"1", "jsonrpc":"2.0", "method": "state_getMetadata", "params":[]}' https://<mainnet | testnet>.creditcoin.network

This will return something like:

{"jsonrpc":"2.0","result":"0x6d6574610b6c185379737....","id":1}

Copy the output to creditcoin.json.

In your src folder, create an interfaces folder and place an empty definitions.ts file in it.

In your packages.json add the following to the scripts section:

"scripts": {
    "build:types": "yarn generate:defs && yarn generate:meta",
    "generate:defs": "ts-node --skip-project node_modules/.bin/polkadot-types-from-defs --package <your project name>/interfaces --input ./src/interfaces --endpoint ./creditcoin.json",
    "generate:meta": "ts-node --skip-project node_modules/.bin/polkadot-types-from-chain --package <your project name>/interfaces  --endpoint ./creditcoin.json --output ./src/interfaces"
  }

Add the following to your tsconfig.json compilerOptions section:

"paths": {
    "@polkadot/api/augment": [
    "./src/interfaces/augment-api.ts"
    ],
    "@polkadot/types/augment": [
    "./src/interfaces/augment-types.ts"
    ],
    "@polkadot/types/lookup": [
    "./src/interfaces/types-lookup.ts"
    ],
}

To generate the types run:

yarn build:types

Code Examples

Many of these examples are adapted from the PolkadotJs API.

Query basic chain information

import { ApiPromise, WsProvider, } from '@polkadot/api';

const main = async () => {
  // Initialise the provider to connect to the either mainnet or testnet rpc node
  const provider = new WsProvider('wss://<mainnet | testnet>.creditcoin.network');

  // Create the API and wait until ready
  const api = await ApiPromise.create({ provider });

  // Retrieve the chain & node information information via rpc calls
  const [chain, nodeName, nodeVersion] = await Promise.all([
    api.rpc.system.chain(),
    api.rpc.system.name(),
    api.rpc.system.version()
  ]);

  console.log(`You are connected to chain ${chain} using ${nodeName} v${nodeVersion}`);
}

main().catch(console.error);

Subscribe and unsubscribe to new blocks

import { ApiPromise, WsProvider, } from '@polkadot/api';

const main = async () => {
  // Initialise the provider to connect to the either mainnet or testnet rpc node
  const provider = new WsProvider('wss://<mainnet | testnet>.creditcoin.network');

  // Create the API and wait until ready
  const api = await ApiPromise.create({ provider });

  // Subscribe to chain updates and log the current block number on update.
  const unsubscribe = await api.rpc.chain.subscribeNewHeads((header) => {
    console.log(`Chain is at block: #${header.number}`);
  });

  // In this example we're calling the unsubscribe() function that is being
  // returned by the api call function after 2 minutes.
  setTimeout(() => {
    unsubscribe();
    console.log('Unsubscribed');
  }, 120000);
}

main().catch(console.error);

More Examples

More examples can be found in the creditcoin-js project.